The invention concerns a mining method, especially for the recovery of useful minerals such as coal, bauxite, etc., from large-mineral deposits, utilizing a caving system of high output, increased concentration of production, and increased safety.
A general requirement of increasing importance in mining is maximising the purity and concentration of the mineral and its output. Thus, mining at reduced production costs without leading to a deterioration of the recovery conditions such as of labour safety and reliability of operation are important goals.
These goals come increasingly into force in the recovery of useful minerals occurring in large deposits in several sections lying side-by-side and/or in several layers. Among such minerals is coal, which is of ever greater importance as an energy carrier.
Large mineral deposits make mass production of great concentration possible. However, in the long term this result can be attained for the most complete possible extraction, that is total working, of the mineral deposits only where the yield of the individual sections and layers is obtained by a modern and suitable mining method, for example mechanical caving and block caving with favourable mining and working conditions and increased safety being guaranteed throughout.
Multi-step exploitation of large-scale mineral deposits conventionally is achieved by leaving behind safety pillars in widths of 100 m or more. The minerals are left in the deposit and then, if necessary, are mined out later or are abandoned in place. This is a particularly prevalent method where the work areas or sections lie side-by-side. On the one hand, these pillars have the task of securing or at least improving the mechanical conditions of working. On the other hand, especially in the case of combustible minerals, the pillars play an important part in the mutual isolation between the individual working areas and sections, as well as in effecting a ventilation seal, whereby the danger and occurrence of endogenous mine fires are considerably reduced.
However, an undoubted disadvantage of mining effected with safety pillars is that the usable mineral in the safety pillar can subsequently only be recovered, if at all, under substantially more difficult conditions and at appreciably greater expense. Where mining takes place in several layers, the mineral cannot safely be recovered. The foregoing not only signifies a great loss of mineral resources, but also is sooner or later detrimental to the conditions of mining the other parts of the mineral deposit.
These conditions arise in all mining methods, i.e., room-and-pillar working, strip working, longwall working, long face working with complex machinery, and also in the case where the usable mineral is won by full-bore (blasting) work; at best, especially in the latter case, the technological and winning disadvantages are less important.
A method is known, for example according to Soviet Pat. No. 589,401, in which an artificial pillar is formed. It is characteristic of this method that it is suitable for exploitation in two layers in the case where a stone band lies between the two seams. The two seams or layers are to be selected so that the stone layer lies between them. The upper layer is extracted by winning in long strips, the roof is secured by anchoring and then a longwall gallery is driven, from which an artificial pillar is formed up to the top of the deposit. Then the lower layer is won and thereupon an overhead cave-in extending to both layers is initiated.
However, the range of utility of this method is limited. The individual technological steps do not render continuous winning possible and in all cases reduce the working output. The method is also costly, since interim securing operations (anchorings) are required which are expensive and complicated in execution and also make the winning more difficult.
An aim of the invention is the development of a method of mining in which the disadvantages of the known methods are eliminated or reduced and which can be used in a wide range for all mineral deposits, especially for mineral deposits of great extent. The present method seeks to enable the recovery to be advantageously cleaner (purer usable mineral), and the production to be more concentrated, less expensive and of increased yield, labour safety and operational reliability.